ACQUAFORTE. – (From the medieval name for nitric acid, aqua fortis). A print produced by means of a copper plate in which the grooves that receive the ink are etched by the action of an acid, rather than directly by the burin as in drypoint (v.). The plate is coated with a layer of wax mixed with resin and then blackened with soot; with a fine point, the subject is incised upon it so as slightly to score the copper, and the plate is then immersed in a solution of nitric acid (the a. of the alchemists), which will bite only the exposed parts of the copper, engraving grooves of varying depth. Once the varnish has been removed, the plate is ready for inking and printing by means of a press. The first proofs are called «avanti lettera». Zinc is easier to work than copper, but less resistant to repeated printing. By using several plates inked in different ways, coloured a. can be produced. Prints are usually signed in pencil.
A. does not possess the formal rigour and precise sharpness of burin engraving; it does, however, permit greater speed, greater freshness, and offers a richer range of chiaroscuro. For these reasons, the burin appears preferable for prints in the classical manner and for precise reproductions.
To promote a. and engraving in general in all its forms, Pope Clement XII established the Calcografia camerale in 1738, acquiring all the copper plates of the De Rossi family. While the use of a. in the field of sacred art is limited to Stations of the Cross, cartouches of glory, images of the crucifix for confessionals, etc., its application in the field of devotional images has been, and may still be, extremely extensive. – Vedi Tav. XVIII.